Accumulators have become known where a piston moves up and down in a housing. Hall sensors outside the housing arranged in a pocket projecting in the interior space of the piston switch on or off a motor via an electric module, depending on the position of the piston.
It is here in particular difficult that in, for example hydraulic cylinders, relatively aggressive oil and typically large pressures occur which make the use of electronic equipment difficult, and that the information about the position has to be carried out through a pressure-resistant wall. Additionally, also the electronic equipment in the interior has to be supplied in some way with electric power.